Error message on cp

[Knute Johnson]

Anybody got any idea why I'm getting this error in my log?

/etc/cron.daily/system-backup:
cp: cannot create regular file 
`/media/usbdisk/home/knute/.cpan/build/Mail-Sendmail-0.79-LupB80/blib/man3/Mail::Sendmail.3pm': 
Invalid argument

The command that generates it is

cp -r /home/knute /someplace

and is run from a cron.daily script.

Thanks,

-- 

Knute Johnson